I really wish I write something down last year!!
It took ages, but finally got it working. They were all going green because the copper oxidised too quickly. This part of raku needs to be starved or oxygen. I was using a pot with airholes because the lid kept popping off.
This works for naked raku where all we need is smoke. For the copper we need smoke and less oxygen!!
So the setup for this is; biscuit tin with holes taped over, and sawdust, item gets dropped in the sawdust, then little ceramic bowl plopped over the item and pished down into the swadust.
Here’s what I managed last year when I worked it out ..
I didn’t coat them with any protective and now, 6 months on they have darkened, but still lovely.
So, new project. I love my tiny pots, but it would be nice to make something functional. So I’m having a go at little ring dishes. Going to finish with copper glaze and then spray with polyurethane varnish to seal and hopefully slow the change to darker.
I took ages because I wanted to print a skull stamp to use on them and my 3d printer was out of action for most of last year.
90mm circle cutter, 60mm skull stamp. 12 flat disks of clay, embossed, left overnight. The next day I curved them on foam with a former. 3 days and a trip to the oven they are bisque-fired.
Problem is, I can’t remember the optimal glazing technique… Certainly, I found out last year, that this copper glaze reacts with unglazed clay and just forms a spiky, bubbly mess. So a layer of black first, but fired or not fired? Can’t remember. I will need to try both.
Decision: it’s doing what it’s supposed to do.
I think it’s doing what it does. Certainly, on unglazed bisque or unfired glaze, it boils and leaves glass bubbles.
Then when you fire too long, you get a green or really dark green, depending on what’s underneath.
I think the one firing last year was a flook, not to be easily repeated. It’s the same glazes, the same clay, the same combustible, but a different scale. Maybe my setup won’t work.
I have seen people have much better success with Copper Penny Mayco, so I will get me some of that and try again.
This is what mayco have for Copper Metalic, it’s not too far from what I have and I noticed that if I go at the surface with wire wool, I see more copper. It’s more moody metal than a shiny penny..
Ok, so I was defeated and gave up. I knew there was something odd about the Vergigris effect I had been getting.
So I ground down the failed first dish above, gave it 3 coats of copper, and tried again. 20 mins, direct into sawdust, and I pushed the cover down and held it there. It worked.
The texture is mostly gone because it’s double-fired, and I threw a bunch of sawdust in the dish before I close it up, so the center is not as coppery, but it’s worked!!
So, after I decided the Copper Metallic was no good for me, I ordered Copper Penny. I have seen this in action (See the wonderful @adamceramic in action: https://www.instagram.com/reel/Cd_hZwPDhCp). Now it took me ages to get the copper metallic to work, so I just assumed the copper penny would work the same. And it did!
Yay! So this is 20 minutes, direct into sawdust, covered to reduce oxygen.
The Copper Metallic reacts badly with my clay body, so I need to glaze it first. All the others have been on black. This time it’s red.
Third success in a row. Getting used to the process. On the left, it’s Copper Metallic, and on the right Copper Penny. Generally, the effect is the same, the penny looks a little lighter. Then we have one coat at the bottom(m1 & p1), 2 in the middle and 3 at the top(m3 & p3). While the 3 coat looks a little fuller, it’s really not much difference to the two coats. The one coat is nice, coppery, but you can see through it.
But most satisfying is the teeth. 2 layers Copper Penny direct on bisque-fired clay. No blistering. This alone makes it the copper of choice for my clay. Also although you can’t see well from this photo it’s a nice yellowy copper. This is great for these little dishes because the 6 layers of glaze is losing the detail.
So parking the Copper Metallic for now, and grabbing the Copper Penny.